How to align lathe headstock/spindle?

[rficalora]

I'm starting to reassemble my lathe; how do I ensure the spindle is parallel to the bed when bolting the headstock back on?

My thought is to get a piece of precision ground round bar that's about 1-1/4" x 24", center it in my 4-jaw (independent) chuck, and then, using an indicator attached to the carriage, zero the indicator near the chuck, move the carriage to the far end, and compare the reading.

Is that a good process? Is there a better way or an accurate way that wouldn't require buying the precision ground bar stock?

 

[projectnut]

Here's a copy of the inspection sheet used for Sheldon lathes. You should be able to perform the same operations on your lathe with a good indicator and test bar.

 

[rficalora]

Here's a copy of the inspection sheet used for Sheldon lathes. You should be able to perform the same operations on your lathe with a good indicator and test bar.

That is great!! Thank you.

Thoughts on using 1045 precision center ground rod as the 12" and 8" "test bars" that they refer to?

 

[projectnut]

I would use a precision test bar for the best results. There are several listed on Amazon and other online retailers. The problem is that if you want to copy the sheet verbatim, you'll be spending a ton of money for what will probably be a single time use tool. You'll need a bar with the headstock taper on one end and the tailstock taper on the other, or 2 independent bars. I haven't done a lot of research, but all those I've found were less than 10" long.

On my lathes the headstocks were pinned in the proper location as well as being bolted to the bed. I took that as the proper location front to back and worked from there. Both have collet draw tube assembles. I installed them and used a 1" diameter dowel pin rather than a test bar for operations that had one free end. Once I was satisfied the headstock was aligned correctly, I used an Edge Technology test bar to align the tailstock. That was the least expensive route at the time. However, I now see the price of larger dowel pins has risen to the point they're almost the same price as the test bars.

When I finished everything was within the specifications listed, but it was probably more due to the work done by the previous owner than myself. The previous owner completely rebuilt the lathe including having the bed and carriage ways ground. He was a retired engineer who spent the majority of his career working for Furnas Electric (now part of Siemens) which supplied the electrical control components for Sheldon. He spent a fair amount of time in the Sheldon plant in Chicago and was intimately involved familiar with the machine. I'm sure he got lots of tips and advice when taking on the project.

 

[homebrewed]

Do a search for RDM, or "Rollie's Dad's Method". It accommodates less-than-perfect test bars. Here is one reference.

I have used it in a couple of applications. One was, of course, to align my headstock to the bed. The second was to check for twist in the bed, by testing the alignment along the bed. It's a good idea to do both so you know exactly what you're dealing with.